Heat treatment is widely used for promoting healing of wounds, burns, ulcers and post-surgically, for treatment of arthritis and muscle-source pain, and for promotion of healing generally. The normal human skin temperature is about 32° C.-33° C., which is a hypothermic temperature compared to normal core body temperature of about 37° C. The hypothermic condition of wounds inhibits healing. Studies have demonstrated that the local application of heat to hypothermic skin will result in some degree of vasodilation, which in turn results in an increase in local blood flow. Increased local blood flow in turn increases both the subcutaneous oxygen level and the availability of blood-borne healing factors, resulting in more collagen deposition and improved immune function. Studies have also demonstrated that temperatures much above the normal core body temperature of about 37° C. result in tissue damage and so do not contribute to promotion of wound therapy and healing.
Many currently available medical devices apply heat to wounds by use of infrared lamps, warm water pads, warm water bottles and by electrically heated pads. Treatment of wounds with infrared light requires that the wound be positioned under the light during therapy, necessitating patient immobility. Infrared light also can result in wounds drying, thereby slowing the healing process. Warm water pads and bottles and electrically heated pads powered by high voltage AC line electrical power transformed to low voltage all restrict patient mobility. In addition, electrically heated pads powered by high voltage AC line electrical power require use of a transformer to reduce voltage to a safe level, and even with such reduction the maintenance of an electrical connection to the high voltage electrical source constitutes a possible danger to patient safety.
A need continues to exist for heatable dressings which can provide a safe and effective level of heating to the skin of a mammalian subject, while being convenient, easy to use, and not restricting the mobility of the mammal to which the dressing is applied.